Even if the flexible, paper-thin screen is the undisputed killer app of display technology, it will never get out of the lab if its tied to present-day battery technology. Batteries have, its true, im
Even if the flexible, paper-thin screen is the undisputed killer app of display technology, it will never get out of the lab if its tied to present-day battery technology. Batteries have, its true, improved dramatically in recent years. Not so long ago mobile phones needed recharging every night. Today, they may last a couple of weeks between charges.
It doesnt have to be like this. Theres a battery technology that stores more power than almost any other, is flexible, extremely lightweight and, like the LEP displays, can be manufactured as a paper-thin sheet and can be cut to any shape or size. Its called the lithium polymer battery.
For any battery, one of the most crucial statistics is how much energy density it can achieve. The more charge that it can squeeze in, the smaller and lighter it will need to be for a given capacity. The best material for achieving high-energy densities is lithium. In its pure form, lithium is a metal and the lightest of all the solid elements. Although not abundant, lithium compounds occur widely within rocks and seawater and are easily extracted. Apart from some specialised uses in areas such as glass manufacture and optical communications, its two main applications are in drugs to treat certain psychiatric disorders, and in the increasingly common Lithium Ion battery.
Lithium Ion is one of the best battery types currently available but falls short
of what could be achieved with metallic lithium. The problem is that metallic
lithium reacts violently with water and may spontaneously catch fire or explode from coming into contact with moisture in the air. Using Lithium Ions is one way of achieving a safe alternative. Another is to bond the lithium to a polymer thats impervious to air and water. Among the polymers that have been used is Kynar resin (also known as PVDF or polyvinylidene fluoride), which is a very stable material and can resist virtually all solvents, acids and other common chemicals.
Lithium batteries comprising several very thin sheets of electrodes separated by a polymer electrolyte have been commercially available for some years now, and theyre rumoured to have been used even earlier in classified devices such as ultra-thin bugs that could be installed invisibly behind wallpaper. The main reason theyre not more widely used is cost, and that comes down to the old chicken-and-egg problem that costs wont fall until demand is high enough, and demand wont rise until the cost falls. Lithium polymer batteries have started to appear in mobile phones, such as Ericssons T28s, and should be ideal for laptops and other portable devices because they can be moulded to any shape, and so can fit snugly inside the casing without requiring a separate compartment.
At the other end of the scale, a heavy-duty form of lithium polymer battery is also being promoted by 3M and Hydro-Quebec to power electric cars. Its claimed to provide over 150 miles of travel before needing recharging, with much less weight and bulk than other battery types. Like all lithium polymer batteries, this one is very thin, consisting of five laminated layers, each just 100 microns thick - the same as cling wrap. This allows dense packing and hence the ability to drive long distances before recharging.
With plastic chips, plastic display screens and plastic batteries, there doesnt seem much more for polymers to muscle in on, but a recent announcement signalled what could be the most important new application of polymers so far. In April this year, a joint team of researchers at the Universities of Washington and Southern California announced that theyd made a major breakthrough in creating an opto-electronic modulator out of plastic.
Modulators act as the interface between the electrical signals used by computers and telephone systems, and the optical signals that travel through fibre-optic cables. Traditionally, theyve been made out of tiny crystals of lithiumniobate, a substance whose optical properties can be varied by applying a voltage to the crystal. The new polymer modulators do the same job, but with at least ten times the bandwidth. Whats more, they require only a fraction of a volt to operate, which means that they consume much less power and generate far
less heat.
Recent tests have shown that a single chip of the new plastic measuring just one micron across can provide more than 300GHz of bandwidth - enough to handle almost a hundred million simultaneous telephone conversations. Or, to look at it digitally, it could transmit about 100Gbytes/sec, which is enough to fill 150 of the latest third-generation trans-atlantic fibre-optic cables. This technology, says Professor Larry Dalton, who is overall leader of the research project, has bandwidth to burn.
In fact, for any practical context that we can currently think of, this is effectively infinite bandwidth. These electro-optic modulators will permit real-time communication, says Dalton. You wont have to wait for your computer to download even the largest files. Of course, this assumes that when the signal moves into the electronic domain theres also enough bandwidth available, which plainly wont be the case with domestic copper telephone lines. For the main Internet infrastructure though, and for businesses with dedicated net connections, it opens up all sorts of sci-fi possibilities. According to Dalton, it could even create the capability for full three-dimensional holographic projection with little or no image flicker. He envisages a Star Trek-type holodeck that could create elaborate virtual worlds in full three-dimensional detail.